7.2.8 Aramid fibers 中英文讲稿

原字幕
中文翻译 In this video, we will study a class of high performance polymeric fibers, aramid fiber. 本节课，我们将学习一类高性能聚合物纤
维，芳纶纤维。

The word aramid comes from aromatic polyamide (芳香尼龙).
芳纶这个词来自芳香聚酰胺(芳香尼龙) Its structure is shown in this picture. The chain molecules in the fibers are highly oriented along the fiber axis. These fibers are based on the amide linkage formed by the reaction between carboxolic
acid and the amine group.
其结构如图所示。

纤维中的分子链沿着纤维轴高度取向排列。

这些纤维基于通过羧酸与胺基之间的反应形成的酰胺键联接。

The picture here shows this reaction. 这里的图片显示了这个反应。

When this linkage occurs between straight-chained-saturated molecules the results are aliphatic amides known commercially as Nylon. One such example is shown in this picture.
当这种连接发生在直链饱和分子之间时，其产物就是脂肪族酰胺，商业上称为尼龙。

这张照片展示了一个这样的例子。

When this linkage occurs between unsaturated benzene rings the results are aromatic amides called aramids, as shown in the picture here. 当这种连接发生在不饱和苯环之间时，产物是芳族酰胺，又称为芳族聚酰胺，如图所示。

The chain molecules of both types of amides are bonded by the ‘hydrogen bonds’ that are subject to disruption by ultra-violet light. The ‘hydrogen-bond’ is shown in here.
两种类型酰胺的分子链通过“氢键”键合，其容易受到紫外线破坏。

图中显示了氢键。

聚酰胺纤维的基本组成物质是通过酰胺键—[NHCO]—连接起来的脂肪族聚酰胺。

当连接的一端是饱和直链碳
链时，所得为尼龙，也成为锦纶。

当连接的一端是不饱和
苯环时，所得为芳族聚酰胺，也就是芳纶。

无论是哪种分
子结构，其分子间都靠氢键连接，较强的氢键作用力也赋
予了聚酰胺纤维优异的力学性能。

Aromatic polyamides were first introduced in commercial applications in the early 1960s, with a meta-aramid fiber produced by DuPont. In 1972, DuPont introduced Kevlar to the market, which is an organic fiber for use in radial tires. This organic fiber
二十世纪六十年代初，芳香族聚酰胺首先应用在商业中，例如由杜邦生产的间位芳族聚酰胺纤维。

1972年，杜邦将凯夫拉纤维投入市场，这是一种用于子午线轮胎
is melt-spun from a liquid polymer solution. 的有机纤维。

这种有机纤维由液态聚合物
溶液熔融纺丝而成。

The aromatic ring structure shown in this figure results in high thermal stability. The rodlike nature of the molecules classifies Kevlar as a liquid-crystalline polymer characterize by its ability to form ordered domains in which the stiff, rodlike molecules line up in parallel arrays. These domains orient and align themselves in the direction of flow during processing causing a high degree of alignment parallel to the fiber axis and resulting in anisotropy, with high strength and tensile modulus in the fiber-longitudinal direction. 图中所示的芳香环结构决定了其高热稳定性。

凯夫拉因其分子的棒状特征被分类为液晶聚合物，其特征在于其形成有序的区域的能力，在其中僵硬的棒状分子以平行阵列排列。

这些区域在加工过程中沿流动方向取向和排列，获得高度平行于纤维轴线的取向并导致各向异性，在纤维纵向上具有高强度和拉伸模量。

These overall properties plus a density of 1.44 g/cm3 (about one-half that of glass) are the key to Kevlar's use in weight-limited applications. In addition, this material is known for its toughness, impact resistance, and resistance to creep and fatigue failure. Even though the aramids are thermoplastics, they are, nevertheless, resistant to combustion and stable to relatively high temperatures; the temperature range over which they retain their high mechanical properties is between minus 200 and 200 degree C. 这些综合特性加上1.44 g / cm3的密度（约为玻璃的一半）是Kevlar在轻质应用中的关键特征。

此外，这种材料以韧性、耐冲击性和抗蠕变和疲劳失效而闻名。

尽管芳族聚酰胺是热塑性塑料，但它们仍然耐燃烧并且在相对较高的温度下稳定；它们保持高力学性能的温度范围在零下200到200摄氏度之间。

凯夫拉纤维密度低、强度高、韧性好、耐高温、易于加工和成型，其强度为同等质量钢铁的5倍,但密度仅为钢铁的五分之一，因此在70年代初被用于替代赛车轮胎中的部分钢材。

Chemically, they are susceptible to degradation by strong acids and bases, but they are relatively inert in other solvents and chemicals. 化学角度上，它们容易被强酸和碱降解，但它们在其他溶剂和化学品中相对惰性。

There are three grades of Kevlar. Kevlar 29 provides high toughness with a tensile strength of about 3.4 目前主要有三个级别的凯夫拉纤维。

凯夫拉29提供高韧性，拉伸强度约为
GPa for use where resistance to stretch and penetration are important. Kevlar 49 has a high-tensile-strength modulus of 130 GPa and is used with structural composites. Kevlar 149 has an ultrahigh tensile modulus of 180 GPa. 3.4GPa，用于抗拉伸和渗透性很高的场合。

凯夫拉49具有130GPa的高拉伸模量，并用于结构复合材料。

凯夫拉尔149具有180GPa的超高拉伸模量。

The figure here is a stress-strain diagram showing the relation of Kevlar 49 to other common reinforcing fibers. 这张图是一张应力-应变图，显示了凯夫拉49与其他常见增强纤维的关系。

The aramid fibers are most often used in composites having polymer matrices; common matrix materials are the epoxies and polyesters. Because the fibers are relatively flexible and somewhat ductile, they may be processed by most common textile operations. 芳族聚酰胺纤维最常用于具有聚合物基体的复合材料;常见的基体材料是环氧树脂和聚酯。

由于纤维相对柔韧并且有点韧性，所以它们可以通过最常见的纺织品操作加工。

Typical applications of these aramid composites are in ballistic products (bulletproof vests and armor), sporting goods, tires, ropes, missile cases, and pressure vessels and as a replacement for asbestos [æsˈbestəs] in automotive brake and clutch linings and gaskets. 这些芳族聚酰胺复合材料的典型应用是防弹产品（防弹背心和装甲），运动产品，轮胎，绳索，导弹和压力容器，以及汽车制动器和离合器衬片和垫片中的石棉替代品。

现在广泛用于船体、飞机、自行车轮胎、军用头盔、防弹背心等。

其主要弱点为于碱性环境下，或暴露于氯及紫外线之下时，将渐渐被分解。

The properties of continuous and aligned glass, carbon, and aramid fiber–reinforced epoxy composites are given in this table. A comparison of the mechanical characteristics of these three materials may be made in both longitudinal and transverse directions. The specific strength of Kevlar 49 fibers are 5 times that of steel. The elongation to failure is a little more than half of that for S-glass but still large compared to carbon fibers. 这张表格中列出了连续且排列的玻璃纤维，碳纤维和芳纶纤维增强环氧树脂复合材料的性能。

这三种材料的力学性能可以在纵向和横向上进行比较。

凯夫拉49纤维的比强度是钢的5倍。

与S型玻璃纤维纤维相比，其断裂伸长率略高于一半，但与碳纤维相比仍然较大。

Ok, in today’s video, we talked about the structure
and properties of aramid fibers, we also talked a
在本节课中，我们学习了芳纶纤维的结构
little bit about its history, finally, we talked about its applications and weakness. 和性能，我们也介绍了一点它的历史，最后，我们学习了它的应用和弱点。

That’s all for today’s course. Thank you.本节课到此结束，谢谢！。